It is known in the automotive instrument panel art to use matrix switching for various ones of the information functions controlled by the driver or a passenger in the vehicle by depressing one or more buttons in a cluster. An exemplary matrix switch in such an application would include, for example, at least four switches, the four switches having two voltage input lines and two strobe lines, with each of the voltage input lines going to two of the switches and each of the strobe lines going to two switches differing in combination than the common input line switches. Thus, for example, the common input lines would go to switches 1 & 3, and switches 2 & 4, respectively, of the four switch matrix, while the common strobe lines would go to switches 1 & 2, and 3 & 4, respectively.
Such strobing determines which one(s) of the exemplary four switches may be closed at any particular point in time. The advantage of such a matrix array is that, rather than requiring, for example, eight independent wires going to the four switches, a total of four is sufficient, two for the input lines and two for the strobe lines.
However, a drawback to such a system is that, should three of the four switches be concurrently closed at any particular point in time, the strobe system would read that all four switches are closed, because of the presence of a feedback loop. In order to avoid this problem, prior circuit design has required that diodes or other unidirectional current flow limiting devices be put in line with the input lines to each of the switches, thus requiring the addition of four diodes to prevent in a 2.times.2 matrix the possibility of such a false signal reading. This obviously causes additional expense in the circuitry and the assembly thereof and adds to the number of electronic components that can malfunction.
Additionally, with respect to the specific application of a button cluster for automotive instrument panel displays, the switching design typically has required independent buttons for the switches, further adding to the cost of the system. An exemplary application is for the automotive or trip information center for an automobile which, upon the actuation of the appropriate button(s), displays such information as the time of day, the odometer reading, fuel consumption rates (instant or average), trip miles to go, average trip speed, estimated time of arrival for the trip in process, etc., with the displays to be either in English or metric units depending upon the user's selection, and with a trip odometer reset button for zeroing the reading. Such an exemplary application in, for example, the "Lincoln Continental Mark VII" has included a cluster array of twelve separate buttons arranged in a single line.
In an exemplary, preferred aspect of the invention, a two "button" rocker switch button structure is used to prevent the concurrent actuation of its two associated switches in order to prevent the possibility of the concurrent actuation of three of the four switches in a 2.times.2 matrix and to achieve economies in the number of button members to be molded, but still maintain the appearance and feel of independent buttons.
As a general proposition, rocker switch actuating mechanisms for controlling a plurality of switches, allowing only one or a preselected number of particular ones, to be actuated is known, noting, for example, the U.S. Pat. Nos. (3,691,324 to Brantingson issued Sept. 12, 1972) and (3,399,287 to Euler issued Aug. 27, 1968).
The Brantingson switch uses a single floating button structure with the external general appearance of two substantially spaced buttons. However, in Brantingson, because of the relatively large spacing between its two external button surfaces on a common button structure, and the fact that it "floats", it is clear to the user that the movement of one obviously and clearly moves the other and that they are, in fact, part of the same integral structure.
In Euler, the whole rocking panel carrying six button surfaces is externally displayed, and the common movement is likewise clearly visible.
Additionally, neither the Brantingson patent nor the Euler patent suggest the use of their rocking switch actuators with a matrix switching system.